FANNING OUT OF THE SOLAR f-MODE IN THE PRESENCE OF NON-UNIFORM MAGNETIC FIELDS?
We show that in the presence of a magnetic field that is varying harmonically in space, the fundamental mode, or f-mode, in a stratified layer is altered in such a way that it fans out in the diagnostic kω diagram, with mode power also within the fan. In our simulations, the surface is defined by a temperature and density jump in a piecewise isothermal layer. Unlike our previous work (Singh et al. 2014), where a uniform magnetic field was considered, here we employ a non-uniform magnetic field together with hydromagnetic turbulence at length scales much smaller than those of the magnetic field. The expansion of the f-mode is stronger for fields confined to the layer below the surface. In some of those cases, the kω diagram also reveals a new class of low-frequency vertical stripes at multiples of twice the horizontal wavenumber of the background magnetic field. We argue that the study of the f-mode expansion might be a new and sensitive tool to determine subsurface magnetic fields with azimuthal or other horizontal periodicity.
- Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)
- Physics Department, Gustaf Hällströmin katu 2a, PO Box 64, FI-00014 University of Helsinki, Helsinki (Finland)
- Publication Date:
- OSTI Identifier:
- Resource Type:
- Journal Article
- Resource Relation:
- Journal Name: Astrophysical Journal Letters; Journal Volume: 795; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
- Country of Publication:
- United States
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLOWERS; COMPUTERIZED SIMULATION; DENSITY; DIAGRAMS; EXPANSION; LAYERS; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PERIODICITY; SPACE; SUN; SURFACES; TURBULENCE